﻿ Python: Find the indices of two numbers that sum to 0 in a given list - w3resource

# Python: Find the indices of two numbers that sum to 0 in a given list

## Python Programming Puzzles: Exercise-29 with Solution

Write a Python program to find the indices of two numbers that sum to 0 in a given list of numbers.

```Input:
[1, -4, 6, 7, 4]
Output:
[4, 1]

Input:
[1232, -20352, 12547, 12440, 741, 341, 525, 20352, 91, 20]
Output:
[1, 7]
```

Pictorial Presentation: Sample Solution-1:

Python Code:

``````#License: https://bit.ly/3oLErEI

def test(nums):
s = set(nums)
for i in s:
if -i in s:
return [nums.index(i), nums.index(-i)]

nums = [1, -4, 6, 7, 4]
print("Original List:")
print(nums)
print("Indices of two numbers that sum to 0 in the said list:")
print(test(nums))
nums=[1232, -20352, 12547, 12440, 741, 341, 525, 20352, 91, 20]
print("\nOriginal List:")
print(nums)
print("Indices of two numbers that sum to 0 in the said list:")
print(test(nums))
``````

Sample Output:

```Original List:
[1, -4, 6, 7, 4]
Indices of two numbers that sum to 0 in the said list:
[4, 1]

Original List:
[1232, -20352, 12547, 12440, 741, 341, 525, 20352, 91, 20]
Indices of two numbers that sum to 0 in the said list:
[1, 7]
```

Flowchart: Sample Solution-2:

Python Code:

``````#License: https://bit.ly/3oLErEI

def test(nums):
result = []
# For each index in the list:
for ind in range(len(nums)):
# For each index in the list:
for i in range(len(nums)):
# If the number at the current index and the other index sum to zero
if ind != i and nums[ind] + nums[i] == 0:
result.append(ind)
result.append(i)
# Found the indices; no need to go through the whole list
return result

nums = [1, -4, 6, 7, 4]
print("Original List:")
print(nums)
print("Indices of two numbers that sum to 0 in the said list:")
print(test(nums))
nums=[1232, -20352, 12547, 12440, 741, 341, 525, 20352, 91, 20]
print("\nOriginal List:")
print(nums)
print("Indices of two numbers that sum to 0 in the said list:")
print(test(nums))
``````

Sample Output:

```Original List:
[1, -4, 6, 7, 4]
Indices of two numbers that sum to 0 in the said list:
[1, 4]

Original List:
[1232, -20352, 12547, 12440, 741, 341, 525, 20352, 91, 20]
Indices of two numbers that sum to 0 in the said list:
[1, 7]
```

Flowchart: Python Code Editor :

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